libstdc++-v3/include/parallel/for_each_selectors.h

   1 // -*- C++ -*-
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   3 // Copyright (C) 2007-2018 Free Software Foundation, Inc.
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  17 // permissions described in the GCC Runtime Library Exception, version
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  24
  25 /** @file parallel/for_each_selectors.h
  26  *  @brief Functors representing different tasks to be plugged into the
  27  *  generic parallelization methods for embarrassingly parallel functions.
  28  *  This file is a GNU parallel extension to the Standard C++ Library.
  29  */
  30
  31 // Written by Felix Putze.
  32
  33 #ifndef _GLIBCXX_PARALLEL_FOR_EACH_SELECTORS_H
  34 #define _GLIBCXX_PARALLEL_FOR_EACH_SELECTORS_H 1
  35
  36 #include <parallel/basic_iterator.h>
  37
  38 namespace __gnu_parallel
  39 {
  40   /** @brief Generic __selector for embarrassingly parallel functions. */
  41   template<typename _It>
  42     struct __generic_for_each_selector
  43     {
  44       /** @brief _Iterator on last element processed; needed for some
  45        *  algorithms (e. g. std::transform()).
  46        */
  47       _It _M_finish_iterator;
  48     };
  49
  50   /** @brief std::for_each() selector. */
  51   template<typename _It>
  52     struct __for_each_selector : public __generic_for_each_selector<_It>
  53     {
  54       /** @brief Functor execution.
  55        *  @param __o Operator.
  56        *  @param __i iterator referencing object. */
  57       template<typename _Op>
  58         bool
  59         operator()(_Op& __o, _It __i)
  60         {
  61           __o(*__i);
  62           return true;
  63         }
  64     };
  65
  66   /** @brief std::generate() selector. */
  67   template<typename _It>
  68     struct __generate_selector : public __generic_for_each_selector<_It>
  69     {
  70       /** @brief Functor execution.
  71        *  @param __o Operator.
  72        *  @param __i iterator referencing object. */
  73       template<typename _Op>
  74         bool
  75         operator()(_Op& __o, _It __i)
  76         {
  77           *__i = __o();
  78           return true;
  79         }
  80     };
  81
  82   /** @brief std::fill() selector. */
  83   template<typename _It>
  84     struct __fill_selector : public __generic_for_each_selector<_It>
  85     {
  86       /** @brief Functor execution.
  87        *  @param __v Current value.
  88        *  @param __i iterator referencing object. */
  89       template<typename _ValueType>
  90         bool
  91         operator()(_ValueType& __v, _It __i)
  92         {
  93           *__i = __v;
  94           return true;
  95         }
  96     };
  97
  98   /** @brief std::transform() __selector, one input sequence variant. */
  99   template<typename _It>
 100     struct __transform1_selector : public __generic_for_each_selector<_It>
 101     {
 102       /** @brief Functor execution.
 103        *  @param __o Operator.
 104        *  @param __i iterator referencing object. */
 105       template<typename _Op>
 106         bool
 107         operator()(_Op& __o, _It __i)
 108         {
 109           *__i.second = __o(*__i.first);
 110           return true;
 111         }
 112     };
 113
 114   /** @brief std::transform() __selector, two input sequences variant. */
 115   template<typename _It>
 116     struct __transform2_selector : public __generic_for_each_selector<_It>
 117     {
 118       /** @brief Functor execution.
 119        *  @param __o Operator.
 120        *  @param __i iterator referencing object. */
 121       template<typename _Op>
 122         bool
 123         operator()(_Op& __o, _It __i)
 124         {
 125           *__i._M_third = __o(*__i._M_first, *__i._M_second);
 126           return true;
 127         }
 128     };
 129
 130   /** @brief std::replace() selector. */
 131   template<typename _It, typename _Tp>
 132     struct __replace_selector : public __generic_for_each_selector<_It>
 133     {
 134       /** @brief Value to replace with. */
 135       const _Tp& __new_val;
 136
 137       /** @brief Constructor
 138        *  @param __new_val Value to replace with. */
 139       explicit
 140       __replace_selector(const _Tp &__new_val) : __new_val(__new_val) {}
 141
 142       /** @brief Functor execution.
 143        *  @param __v Current value.
 144        *  @param __i iterator referencing object. */
 145       bool
 146       operator()(_Tp& __v, _It __i)
 147       {
 148         if (*__i == __v)
 149           *__i = __new_val;
 150         return true;
 151       }
 152     };
 153
 154   /** @brief std::replace() selector. */
 155   template<typename _It, typename _Op, typename _Tp>
 156     struct __replace_if_selector : public __generic_for_each_selector<_It>
 157     {
 158       /** @brief Value to replace with. */
 159       const _Tp& __new_val;
 160
 161       /** @brief Constructor.
 162        *  @param __new_val Value to replace with. */
 163       explicit
 164       __replace_if_selector(const _Tp &__new_val) : __new_val(__new_val) { }
 165
 166       /** @brief Functor execution.
 167        *  @param __o Operator.
 168        *  @param __i iterator referencing object. */
 169       bool
 170       operator()(_Op& __o, _It __i)
 171       {
 172         if (__o(*__i))
 173           *__i = __new_val;
 174         return true;
 175       }
 176     };
 177
 178   /** @brief std::count() selector. */
 179   template<typename _It, typename _Diff>
 180     struct __count_selector : public __generic_for_each_selector<_It>
 181     {
 182       /** @brief Functor execution.
 183        *  @param __v Current value.
 184        *  @param __i iterator referencing object.
 185        *  @return 1 if count, 0 if does not count. */
 186       template<typename _ValueType>
 187         _Diff
 188         operator()(_ValueType& __v, _It __i)
 189         { return (__v == *__i) ? 1 : 0; }
 190     };
 191
 192   /** @brief std::count_if () selector. */
 193   template<typename _It, typename _Diff>
 194     struct __count_if_selector : public __generic_for_each_selector<_It>
 195     {
 196       /** @brief Functor execution.
 197        *  @param __o Operator.
 198        *  @param __i iterator referencing object.
 199        *  @return 1 if count, 0 if does not count. */
 200       template<typename _Op>
 201         _Diff
 202         operator()(_Op& __o, _It __i)
 203         { return (__o(*__i)) ? 1 : 0; }
 204     };
 205
 206   /** @brief std::accumulate() selector. */
 207   template<typename _It>
 208     struct __accumulate_selector : public __generic_for_each_selector<_It>
 209     {
 210       /** @brief Functor execution.
 211        *  @param __o Operator (unused).
 212        *  @param __i iterator referencing object.
 213        *  @return The current value. */
 214       template<typename _Op>
 215         typename std::iterator_traits<_It>::value_type
 216         operator()(_Op __o, _It __i)
 217         { return *__i; }
 218     };
 219
 220   /** @brief std::inner_product() selector. */
 221   template<typename _It, typename _It2, typename _Tp>
 222     struct __inner_product_selector : public __generic_for_each_selector<_It>
 223     {
 224       /** @brief Begin iterator of first sequence. */
 225       _It  __begin1_iterator;
 226
 227       /** @brief Begin iterator of second sequence. */
 228       _It2 __begin2_iterator;
 229
 230       /** @brief Constructor.
 231        *  @param __b1 Begin iterator of first sequence.
 232        *  @param __b2 Begin iterator of second sequence. */
 233       explicit
 234       __inner_product_selector(_It __b1, _It2 __b2)
 235       : __begin1_iterator(__b1), __begin2_iterator(__b2) { }
 236
 237       /** @brief Functor execution.
 238        *  @param __mult Multiplication functor.
 239        *  @param __current iterator referencing object.
 240        *  @return Inner product elemental __result. */
 241       template<typename _Op>
 242         _Tp
 243         operator()(_Op __mult, _It __current)
 244         {
 245           typename std::iterator_traits<_It>::difference_type __position
 246             = __current - __begin1_iterator;
 247           return __mult(*__current, *(__begin2_iterator + __position));
 248         }
 249     };
 250
 251   /** @brief Selector that just returns the passed iterator. */
 252   template<typename _It>
 253     struct __identity_selector : public __generic_for_each_selector<_It>
 254     {
 255       /** @brief Functor execution.
 256        *  @param __o Operator (unused).
 257        *  @param __i iterator referencing object.
 258        *  @return Passed iterator. */
 259       template<typename _Op>
 260         _It
 261         operator()(_Op __o, _It __i)
 262         { return __i; }
 263     };
 264
 265   /** @brief Selector that returns the difference between two adjacent
 266    *  __elements.
 267    */
 268   template<typename _It>
 269     struct __adjacent_difference_selector
 270     : public __generic_for_each_selector<_It>
 271     {
 272       template<typename _Op>
 273         bool
 274         operator()(_Op& __o, _It __i)
 275         {
 276           typename _It::first_type __go_back_one = __i.first;
 277           --__go_back_one;
 278           *__i.second = __o(*__i.first, *__go_back_one);
 279           return true;
 280         }
 281     };
 282
 283   /** @brief Functor doing nothing
 284    *
 285    *  For some __reduction tasks (this is not a function object, but is
 286    *  passed as __selector __dummy parameter.
 287    */
 288   struct _Nothing
 289   {
 290     /** @brief Functor execution.
 291      *  @param __i iterator referencing object. */
 292     template<typename _It>
 293       void
 294       operator()(_It __i) { }
 295   };
 296
 297   /** @brief Reduction function doing nothing. */
 298   struct _DummyReduct
 299   {
 300     bool
 301     operator()(bool, bool) const
 302     { return true; }
 303   };
 304
 305   /** @brief Reduction for finding the maximum element, using a comparator. */
 306   template<typename _Compare, typename _It>
 307     struct __min_element_reduct
 308     {
 309       _Compare& __comp;
 310
 311       explicit
 312       __min_element_reduct(_Compare &__c) : __comp(__c) { }
 313
 314       _It
 315       operator()(_It __x, _It __y)
 316       { return (__comp(*__x, *__y)) ? __x : __y; }
 317     };
 318
 319   /** @brief Reduction for finding the maximum element, using a comparator. */
 320   template<typename _Compare, typename _It>
 321     struct __max_element_reduct
 322     {
 323       _Compare& __comp;
 324
 325       explicit
 326       __max_element_reduct(_Compare& __c) : __comp(__c) { }
 327
 328       _It
 329       operator()(_It __x, _It __y)
 330       { return (__comp(*__x, *__y)) ? __y : __x; }
 331     };
 332
 333   /** @brief General reduction, using a binary operator. */
 334   template<typename _BinOp>
 335     struct __accumulate_binop_reduct
 336     {
 337       _BinOp& __binop;
 338
 339       explicit
 340       __accumulate_binop_reduct(_BinOp& __b) : __binop(__b) { }
 341
 342       template<typename _Result, typename _Addend>
 343         _Result
 344         operator()(const _Result& __x, const _Addend& __y)
 345         { return __binop(__x, __y); }
 346     };
 347 }
 348
 349 #endif /* _GLIBCXX_PARALLEL_FOR_EACH_SELECTORS_H */